Electrical heating element



May 5, 1953 P. SCHENK ELECTRICAL HEATING ELEMENT Filed Sept. 27, 1951 INV EN TOR.

Patented May 5, 1953 UNI TE D S TAT i2 S @AT ENT (DEF ICE ELECTRICALHEATING ELEMENT 'Peter Schenk,.South ()zoneiPark, N. Y.

Application September 27, 1 951, Seriall'No. 248,548

6 Claims.

' Thisxinventionirelates to 'electrical heating elements, andparticularly to those of rod-like for- :mation, in .which .a iheatingfilament is enclosed within an outer metalliclsleeve andwithaninterposed-insulating andheat conductingmaterial lo- ;oated between131160111381 sleeve and the filament.

It is an object of the invention to provide an article of this characterin whicha maximum of protection for the heating filament is provided; inwhich the filament is so enclosed and protected that contact with airand with resultant oxidation will be prevented and as result the life ofthe heating element materially increased.

It is another object of the invention to provide .an improved method bywhich heating elem :lts

.can be manufactured easily and inexpensively; it ,is an-objectof theinvention to provide a heat- .ing element which can be made in varioussizes and shapes to suit different requirements, and one which willstandhigh temperatures for long periods of use.

More particularly, the invention contemplates the provision ofa heatingelement consisting or a filament surrounded by and spaced from ametallic sleeve, with the space between the sleeve and the.filamentcompletely filled with glass, the glass closely surrounding thefilament and maintaining it centrally in .the sleeve and out of contactwith the walls of the sleeve. The invention turther contemplates theprovision of a method of making such a heating element wherein thefilament is surrounded by a glass tube and the glass tube is enclosed inthe outer metallic sleeve, and heating means travelling the length ofthe sleeve applies heat to the glass tube to render the same moltenwhile longitudinal pressure is applied to the glass tube so that as thesame is melted by the heat it fills the .entire interior of the sleeveand closely surrounds the filament and holds it centrally of the sleeveand free from contact with the inner wall surfaces thereof.

With these and other objects tobe hereinafter set forth, in view, I havedevised the particular arrangement of parts to be described and morespecifically pointed out in the claims appended hereto.

In the-accompanying drawing, wherein an illustrative embodiment of theinvention is disclosed,

Fig. l is an .elevational view, with parts broken away and other partsin section, of an electrical heatingelement made according to theinvention;

.Fig. 2 is a View showing the manner in which the heating element ismade;

Fig. 3 is a sectional view takenon the line 3-3 of Fig. 1;

Fig.4 is a View of one of the heating elements of straight formation;and v Fig. 5 shows a heating element in the form of a loop.

Referring to the drawing, I indicates the filament of the heatingelement, which filament may 2 be of Nichrome wire or other suitablematerial. In the form shown, the filament is spiral or helical andateachotitsends itis attached-to the"terminals.indicatedrespectivelyiatfi:and3. These terminals may bemetallic rods :or wires randumay be welded or otherwise securelyattached "to the opposite ends of the filament "coil :I, or :may befrictionally held within t: e spirals of the :coil :by a tight fittherein.

The outside :casingor covering "of the heating element consists of ametallic sleeve or tube 5 which has an inside diameter considerablylarger than the diameter of the filament coil I so that when thefilament is inserted within the itubeor sleeve an annular space isprovided within the tube 5 between the inner wall surface :of theIsaidtube and the filament coil I. Thisspa'ce is filled with glass or othersuitable insulatingmateria-l capable of withstanding heat and becomingplastic under high temperature. This filling -.8 is such as tocompletely fill the interiorof the metal tube or sleeve 5 and to extendbetween the-convolutions of thefilarnent coil and thus completelyenca-se the coil well assurround the inner ends of the terminals 2andfi.

The method b .which the improved heatin elementismade is clearly shownin Fig. 2. Ampport or base is shown at 52 and .thesame is provided witha recess orseat I3 in which one endof the metal tube or sleeve jEisseated. A glass tube 8 is inserted concentrically within themetal tube 5and said glass tube has one .end resting upon theseat l3. Insertedwithin the glass tube 3Listhe filament l having the attached endterminals 2 and 3 which protrude out of the opposite ends of theconcentric sleeves'E and 'B,;the.lower terminal, or that indicated atextending down through the seat i3 and out of the .bore I54 leadingtherefrom.

A weight or other pressure imposing element! is placed against theexposed end of the glass tube 8 and the weight I exerts pressuredownward, or in the direction of the arrow indicated at H. While suchpressure is being exerted against one end'of the glass tube 8, a heatingdevice, such "as one or more jets projecting gas flames, is directedagainst'the outer tube 5, beginning at the lower end of the'same, andisslowly moved upwardly, in the direction of thearrow It. he heat from theburner 9 will melt the glass tube, causing it to become plastic ormolten and completely fill the interior of themetal tube 5 and flowaround the filament I and enter between the convolutions thereof andthus .completely encase the filament and hold it centrally within andspaced from the outer tube 5. The pressure exerted by the weightor;pressuremeans -I, longitudinally of the glass-tube 8, while the heatsource 9 travels in an opposite direction, causes the glass or fillingmaterial 4 to be compacted in the tube 5 and thus caused to fill all ofthe space within the tube and completely surround and encase thefilament I.

When the heating element is used, it will be apparent that the glassfilling will become plastic or softened by the heat of the filament l,but the filling material 4 will not become sufficiently molten to flowout of the ends of the tube 5, for the reason that the filamentterminates short of the ends of the tube 5 and thus the end portions ofthe glass filling, indicated at 6, 6 in Fig. 1, do not become hot enoughto fiow out or permit the passage of the hotter central portion of theglass filling 4. Of course, closure caps might be provided at theopposite ends of the sleeve or tube 5 to hold the glass filling in placeshould such end-closure means be found desirable.

The resultant heating element, made according to the method abovedescribed, can be made in various shapes and forms, the same being shown'in the form of a straight rod in Fig. 4 and in loop shape in Fig. 5.The element may be readily bent in various forms, and while the glassfilling might break or shatter when the element is so bent, the brokenportions will merge together when the element is heated and glassbecomes molten or plastic under the heat. Since the glass filling 4completely surrounds and encases the filament at all times, air cannotreach the filament and thus oxidation is prevented.

One of the difii'culties encountered in making heating elements in whicha filament is contained within an outer metallic shell and a powderedmaterial is deposited within the shell and about the filament, is themaintenance of the filament centrally and away from the side Wall of theouter metallic shell during the filling operation. Such a difficulty iscompletley obviated with the present structure since the glass tube 8,inserted within the metallic shell 5 and SUTTOUIIL. ing the filament I,will hold the filament centrally during the manufacture of the elementby the method described.

In describing the method of making the heating element, I have suggestedthat it be done while the tubes 5 and 8 are maintained vertically, butit will be apparent that this method may be carried out with the tubesarranged horziontally or in other positions. In addition to suportingthe tubes 5 and 8 at one end on the seat :3, these tubes may besupported along their length as required, during the application of theheat by the burner 9, and during the simultaneous application of thepressure at one end of the glass tube 8. Also while I have herein shownthe filament as being of helical or spiral form, it will be apparentthat the same may be straight or otherwise shaped to suit variousrequirements.

Having described one embodiment of the invention, it is obvious that thesame is not to be restricted thereto, but is broad enough to cover allstructures coming within the scope of the annexed claims.

What I claim is:

1. The method of making a heating element comprising, the steps ofsurrounding a filament with a glass tube, encasing the glass tube withina metal tube, applying travelling heat longitudinally along the metaltube to heat the same and thereby melt the glass tube within said metaltube, and applying longitudinal pressure to the glass tube duringapplication of the heat so that as the glass tube melts the entireinterior of the metal tube is filled with molten glass encasing thefilament.

2. The method of making a heating element comprising, surrounding afilament with a glass tube, surrounding said glass tube with a metaltube, progressively heating the glass tube to melt the same inside ofthe metal tube and cause the same to fiow around the filament and fillthe space between the filament and the interior of the metal tube andapplying pressure longitudinally of the glass tube during theapplication of the heat.

3. The method of making a heating element comprising placing a glasstube within a metal tube and around a filament located within the metaltube to thereby position the glass tube between said filament and metaltube, and heating the glass tube while applying pressure to the same tocause it to fiow about the filament and completely fill the spacebetween the filament and the interior of the metal tube.

4. The method of making a heating element comprising, placing a glasstube within a metal tube and around a filament located within the metaltube to thereby position the glass tube between the filament and themetal tube, heating the glass by heating means travelling the length ofthe tube to thereby render the glass tube molten and cause it tocompletely fill the space between the filament and the interior wallsurfaces of the metal tube, and applying pressure in a direction axiallyof the glass tube during the application of the heat.

5. The method of making a heating element comprising, surrounding aspiral filament with a glass tube, surrounding said glass tube with ametal tube, progressively heating the glass tube by travelling heatingmeans moving from one end of the glass tube to its other end to therebymelt the glass tube inside of the metal tube and cause the molten glassto fiow around the filament and fill the space between the filament andthe interior of the metal tube, and applying pressure on the tube in adirection opposite to the direction of movement of the travellingheating means while the glass tube is being heated thereby.

6. The method of making a heating element comprising surrounding afilament with a glass tube, surrounding the glass tube with a metaltube, applying pressure on one end of the glass tube while applying heatagainst the glass tube with the source of heat movable in a directionopposite to the direction of imposed pressure on the glass tube.

PETER SCHENK.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 761,204 Carpenter May 31, 1904 845,413 I-Iaagn Feb. 26, 19072,216,375 Minter Oct. 1, 1940 2,419,655 Reiser Apr. 29, 1947 2,444,410Keinath June 29, 1948 2,566,335 Joerren Sept. 4, 1951 OTHER REFERENCESReview of Scientific Instruments, August 1947, pp. 591-2.

